Stub on end of shaft and bushing in flywheel is only needed when lineing up shaft to engine. Once shaft is lined up and nothing is changed to cause a need for realigning the stub and bushing need not be there just like slightly newer machines than what you have. Other than very high hours the only thing that shortens life of flex plate is misalignment. If you fell you didn't get good life out of flex plate you need to have it aligned and the service manual has very good info on this. looks for cracks coming from spring area if going to a recker for that is sign of very old or misaligned shaft and damaged plate. Good luck